Electrical measuring instrument.



PATENTED JUNE 12, 1905.

F W. ROLLER ELECTRICAL MEASURING INSTRUMENT.

APiLIBLTIfiH FILED JULY 18. 1904.

B BHEETB-SHEBT 1.

WITNESSES:

JUORNH No. 822,987. PATENTED JUNE 12, 1906 F. W. ROLLER. ELECTRIGAL MEASURING INSTRUMENT.

APILIOATIOR FILED JULY 18, 1904.

2 SHEETS-SHEET 2 gag/fi w. m

UNITED STATES PATENT OFFICE.

FRANK W. ROLLER, OF PLAINFIELD, NEW JERSEY.

ELECTRICAL msasunmemsrnumen'r.

To all whom it may concern:

Be it known that I, FRANK. W. Rouse, a citizen of the United States, residing at Plainfield, in the county of Union and State of New Jersey, have invented certain new and useful Improvements in Electrical Measuring Instruments, of which the following is a full, clear, and exact specification.

My invention relates to electrical measuring instruments, and particularly to that type for measurin current or volta e in which t e movement the pointer is etermined by the expansion of a wire heated'by current passing through the instrument.

The object of my invention is the production of an instrument which will have a high degree of accuracy, be free from any ossibihty of injury from excessive overlo s, be capable of use in any convenient position, be unaffected by changes in temperature of the surrounding medium, unaffected by any when placedneighboring magnetic field as near dynamo-electric machines, and overcome various objections to instruments previously used. i

My invention will be understood by refer:

ence to the following descriptionand accompanying drawings, which show the preferred orm 0 my invention, and will be more particularly set forth in the claims. V

Figure 1 is a plan view of an instrument embodying my invention with the case removedand part of the scalelate broken away. Fi 2- is a section on t e line 2 2 of Fig. 1.

Fi .5 and 6 are gs gs. 3 and 4 are details.

an and end views respectively,

of a modified arrangement 0 the tensionwires. Fig. 7 illustrates diagrammatically my improved short-circuitin device. 8 and 9 show modifications t erect. 'Fig. i0

par y broken away and provided with my improved short-circuiting device. Fig. 11 1s a similar view of a modification.

The base of the instrument is indicated at 1 and within this'may be located, if desired the shunt which carries the main portion 0 the current when the instrument )8 used as an ammeter or the high-series resistance when used as a voltmeter. To the base 1 is secured a metal plate 2, upon which the workmg parts of the instrument are mounted. From the post 3, which is secured to the plate 2, extends a thin strip of metal 4, and at right angles thereto is secured the tension-plate 5. The edges of the strip 4 are clamped 1n slots Specification of Letters Patent.

- L lppliostlon filed July 18, 1904. Burial Ho. 216,946.

Figs.

is atplen view of an instrument with the case Patented June 12, 1906.

cut in the post3 and plate 5, or the parts may be secured in any other desired manner. 1 The late ma be supported on a knife-edge or "by a flexib e strip at the ogposite side of 0st 3 to that shown on the rawings, in w 'ch case the flexible strip would be in tension. A spiral spring 6 is connected by a pin 7 to the p ate 5 stone end, and at the other end of the s ring is secured a screw 8, which passes through a fixed post 9 and into a thumb-nut sion of the spring.

A second 'post'll on the plate 2 hasfixed thereto two thin metal stri s 12, which su port at their outer ends t e in 13. T e stri an pass through slots in pin 13, the outer ends of the strips being expanded but these partsmay be secured in any other convenicntn anner. A wire in two parts, 14 14 is secured at one end 15 to the plate 5, passes around the pin 13 between thetwo strips 12 in the form of a thin strip 16, and isseeured at itsjopposite end 17 to the plate 5.. One ends? the wire 15 makes electrical contact with the late 5, and the other end 17 is insulated. r e two ends 15 17 lie in a vertical plane, as shown in Fig. 1, and the part 16 s secured to pin 13, as by soidermg. A flexible connection 18 is made from part 14 of the wire to a 19, which passes down through the plate being insulated therefrom b the bushing 20, and connection is made in t e base of the instrument from the in20 to A value 23 is ed to, the pin 13, being 25 is pivoted between two gewels, one in the extending from postB. Upon t e shaft 25 is 28, one end of this fiber being attached to .vnne 23, and the other end to a spring 28, which latter is'sup'ported b a pin 28 from plate}, and which tends to cop a sh ht tension on fiber 28. The fiber is attach to the slBQYQZ'Z at one oint, as by a screw 29. l to the s aft by the nuts 36 is an indi- .cating-needle 31, which extends over a suitably-calibrated scalesplate 32. is counterbalanced by the we ht 33. Also carried by shaft 25 is a thin k 34 of aluminium orother non-m etic good conducting metal, which exten s between the two po as 35 of the U-shaped permanent magnet 10, so that turning the nut 10 varies the ten- 12 are soldered into a. 5 0t in post 11 one'terminal 21 of the instrument, t e other terminal 22 bein connected to the plate 2. I

counterbalanced by the weights 24. A shaft 7 plate 2 and the other carriedb an arm 26,-

fixed a sleeve 27, whicheis encircled by a fiber e needle IIO 36, which arran ement tends to dampen the movement of t e needle, as is well understood. I

When no current passes through the instrument, the pin 13 is in what may be termed a central position, and the tension on the wires 14 14 is equal. This tension is adjustable to any desired amount by turning the thumb-nut 10, and so var the tension on spring 6. As the ends 15 an 17 of the wires 14 14 lie in the same vertical plane, any increase in tension on the wires by the force of spring 6 is shared equally and there is no tendenc to change the position of pin 13.

he path of the current through the instrument is from terminal 21 to pin 19, lead 18 to wire 14, and then divides and passes through the two halves of wire 14 in parallel and through the supportin parts to plate 2, and then to terminal22. he passing of the current heats the wire 14 to a temperature depending upon the strength of the current, which causes the wire to expand correspondingly. When the wire 14 expands, the pin 6 13 will be turned slightly by reason of the pull exerted by spring 6 upon the wires which tends to equalize their tension. Hence as wire 14 becomes extended in len th the pin 13 will be turned by the pull of wire 14 until the tension in the two wires becomes equal. The amount the pins turn therefore correctly indicates the strength of the current passing in the instrument. Such motion is reproduced and greatly am. lified in the movement of the indicating-nee e by the vane 23, fiber 28, and shaft 25; My improved instrument is not affected by any change in the temperature of the sur rounding medium, as the wires 14 and 14, being of the same material and same length, will expand and contract an equal amount upon any change in temperatureof the whole instrument, which equal expansion or contraction will be taken up or allowed for by the spring 6 without any change in the position of the indicating-needle.

The form above described is suitable for an ammeter, as the two halves of the wire 14 in parallel have a comparativelly low resistance, and for the measurement of arge current the instrument is placed in parallel with a lowresistance shunt.

A modified arran ement of the wires is ineated in Figsf5 an 6, which arrangement is more suitable for a voltmeter. In a voltineter the current assing is usually so small that in order to o tain the necessary expansion the cross-section, of the wire required is so much reduced that it may not have sulficient mechanical strength. I therefore use in the modified construction referred to two very small wires in screen To the late 5 are secured, as before,ethe ride of the wires 14 14, which extend to the pin 13. A second pair of wires 37" 37 are alsoseeured to the plate 5 time with the ends 38 39' in the same vertical plane and pass to the pin 13 and arranged similarly to wires 14 14. With this modified construction the ends 15, 17, 38, and 39 are insulated from plate 5 and the pin 13 or its su port is also insulated. The current is lead rom one terminal of the instrument by wire 40 to the end 15 and passes through wire 14 to pin 13, which, as stated,-is insulated from the plate 2, and the current then passes back through the wire 37 to the end 38 and then by wire 41 to the other terminal of the instrument. As the wires 14 and 37" pass to the same side of pin 13 and each carry the same current, the two pairs of wires act to deflect the needle in the same manne as the wires 14 14'.

If desired, the pin 13 may be in the form of a vertically-pivoted shart, but with such an arrangement the friction of the pivoted shaft due to the side pull of the wires would be objectionable.

I also provide specialmeans for protecting the instrument from excessive overloads. A large overload may not only cause the burnin out of the instrument, but with this artitu ar type of instrument excessive overoads are objectionable, as if the currentcar- 'ng Wire is overheated the physical properties of the wire are changed to some degree, which may sli htly affect the accuracy of the instrument. T therefore introduce a device by which the current is shunted when the value of the same exceeds a certain amount.

This device may be used upon any type of instrument, but is particularly desirable in connection with hot wire instruments. My safety device is illustrated -in Figs. 7, 8, and 9, and is not shown on Figs. 1 and 2, to avoid confusion of the drawings. In a suitable position on the instrument I mount a shortcircuiting device in the path of the needle, so

that when the needle attains its maximum deflection it will cause the instrument to be short-eircuited.

Referring to Fig. 7 there is illustrated a small block of insulatin material 37, carrying a pin 38, upon whic is hinged the metal strip 39, carrying at its extremity the contact-piece 40. The strip 39 is pressed against a stop 41 by a light s ring 42, both 0 which are mounted upon t iie insulatingblock 37 in any convenient manner. A second strip43 is mounted upon the block 37, and carries a contact 44, facing thg contact 40. Connection is made from the terminals 21 22 of the instrument to the strips 39 and 43, as indicated by the wires 45. The block 37 is so located on the instrument that the hinged strip 39 is in the path of the indicating-needle 31, so that when the needle reaches the maximum deflection it. strikes against the plate 39 and moves the same against the pressure of spring 42. This causes the engagement of contacts 40 and 44 position to an insu and a direct path for the current is made be ward'the zero position of the scale and the contacts 40 and 44 will separate. This causes the full current to again pass through wire 14, and unless the overload were removed the needle would continually cause the making and Breaking of the circuit through the wire 45.

Fig. 8 illustrates an arrangement in which the short circuit through wire 45 is maintained until broken by the operator or by failure of current. In Fi 8 the parts are similar to those shown in ig. 7, except that the coil 46 of the electromagnet is included in the circuit 45,. The electromagnet has a pivoted armature 47 electrically connected with terminal 21 through switch 48. When the armature 47 is attracted against gravity or the spring 49, it engages the contact 50, which is electrically connected with wire 45 at 51 When the contacts 40and 44 are -brought into engagement, as above explained, the current in passmg through wire 45 will energize the eleetromagnet 46 and the armature 47 will be attracted. A circuit will then be made from terminal 21, through switch 48, armature 47, to contact 50, coil 46, and then to terminal 22. short circuit will then be maintained even when the needle falls toward its zero position and when the contacts 40 44 are separated. When the switch 48 is o ened, the armature 47 will be moved away om contact 50, and the switch may again be closed, thus placing the instrument in operative condition. Fig. 10 shews the contacts 40 44 located in the path of the indicating-needle 31.

Fig. 9'illustrates an arrangement similar to that shown in Fig: 8, except that the switch 48 is replaced by a switch which is automatically openedby the indicating-needle. On

atingb ock 152 are mounted the two eonductin -strips 53 54 which are in enement' y reason of the strip 53 pressing ig tly against the end of strip 54. These parts are so mounted on the instrument that the strip 53 is in the path of the needle when it reaches the zero-point, and the strips 53 and 54 are then disengaged. This will cause armature 47 to be moved away from contact 50, and current ma then ass through the conductor '14, as be ore. ith this arrange ment the needle will fluctuate from the zero the maximum deflection until the F 11 shows the conoverload is removed.

in the path of the tacts 40, 44, and 53 loca indicating needle 3 1 Although. I have shown and described a are connected, yieldable means to which the opposite ends of said wires are connected,

and means for multi lying and transmitting the movement of sai movable element to an indicating-needle, substantially as described. 2. In anelectrical measuring instrument,

' the combination of a current-carrying wire, a

com ensating wire, a movable element to whic said wires are connected, yieldable means for placing tension on said wires, a vane carrie by said movable element, a pivoted indicating-needle, and a. fiber engaging the shaft of said needle and attached to one end of said vane.

3. In an electrical measuring instrument, the combination of a current-carrying wire a compensating wire, a movable element to t e opposite sides of which two ends of said Wires are connected, yieldable means to which the opposite ends of said wires are connected, a vane carried by said movable elewent, a. pivoted indicatin -needle, and a fiber en aging the shaft 0 said needle and attached to one end of said vane substantially as described.

4. In an electrical measuring instrument, the combination of a current-carrying wire, a compensating wire, a movable element to the opposite sides of which two ends of said wires are connected, yieldable means to which the opposite ends of said wires are connected, a dampening device, and means for mdicating the movement of said movable element, substantialiy as described. I

5. In an electrical measuring instrument, the combination of a current-carrying Wire'- and a compensatin wire, a movable element to the opposite si es of which two ends of said wires are connected, aipivoted member to which the other two ends of said wires are connected, a spring connected to said pivoted member, and means for indicating the movement of said movable element, substantially as described.

6. In an electrical measuring instrument, the combination of a current-carrying wire a compensating wire a movable element to t e opposite sides of whichtwo ends of said wires are connected, yieldable means for placing tension on said wires, a pivoted shaft carrying an indicating-needle, a vanecarried by said movable element, and a fiber connect ng said vane and said shaft, substantially as described.

7. In an electrical measuring instrument,

the combination of a current-carrying Wire and a compensatin Wire, a movable element to the opposite si es of which two ends of said wires are connected, yieldable means for placing tension on said wires, a dampening device, a pivoted shaft carrying an indicating-needle, a vane carried by said movable element, and a fiber connectin said vane and shaft, substantially as descri ed.

8. In an electrical measuring instrument, the combination of a current-carrying wire and a compensatin wire, a movable element to the opposite si es of which two ends of said Wires are connected, a pivoted member to Which the other two ends of said Wires are connected, a spring connected to said pivoted member, a pivoted shaft carrying an indicating-needle, a fiber for turning said pivoted shaft, and a vane carried by said movable element to which vane the said fiber is connected, substantially as described.

9. In an electrical measuring instrument, the combination of a current-carrying wire and a compensating wire, a movable pin on the opposite sides of which two ends of said wires are connected, a ivoted member to which the other two-ends of said wires are connected, a spring connected to said pivoted member, and means for multiplying and transmitting the movement of said movable pin to an indicating-needle, substantially as described.

10. In an electrical measuring instrument, the combination of a current-carrying wire, a compensating wire, a movable element to the opposite sides of which two ends of said'wires are connected, yieldable means for placing tension on said wires, a pivoted shaft carrying an indicating-needle, a conductor carried by said shaft, means for producing a magnetic field in the presence of said conductor,

and means for transmitting the movement of said movable element to said shaft.

11. In an electrical measuring instrument,

the combination with the current-carrying part, of means in the path of the indicatingneedle for short-circuiting said part.

12. In an electrical measuring instrument, the combination with the current-carrying part, of means in the path of the movable indieatin part for automatically short-circuiting said current-carrying part upon the occurrence of excessive current through the instrument.

13. In an electrical measuring instrument, the combination with the current-carrying part, of means for automatically shortcircuiting said part upon the occurrence of excessive current through the instrument, and means for maintaining the short circuit.

14. In an electrical measuring instrument, the combination with the current-carrying part, of means for short-circuiting said part upon the occurrence of excessive current throu h the instrument and for maintaining said sliort circuit, substantially as described.

15. In an electrical measuring instrument, the combination with the current-carryin part, a relay device for short-circuiting sai part, and means in the path of a movable part of said instrument for operating said re ay upon the occurrence of excessive current through theinstrument.

16. In an electrical measuring instrument, the combination with the current-carrying part, of means for short-circuiting said part upon the occurrence of excessive current through the instrument, and means for removing the short circuit when the indicating part returns to its initial osition.

In testimony whereof affix my signature in presence of two Witnesses.

FRANK W. ROLLER. 

